An interdisciplinary group has developed an improved mechanical left ventricular assist pump. This device is fabricated of a smooth segmented polyurethane sac within a rigid plastic housing. Ball-type inlet and outlet valves are employed. The device has been employed in a series of normal calves and has been found to be safe and effective. Additional experience will be gained over the next year in the use of this improved assist pump in normal calves. In addition, a program has been undertaken in which the left ventricular assist pump will be employed in calves who have sustained myocardial infarction by the injection of 10 micron diameter microspheres into the left coronary artery. When severe cardiogenic shock has been produced, with a systolic arterial pressure less than 60 and a left atrial pressure greater than 25mmHg, left ventricular assist pumping will be initiated. Studies will be carried out to determine the time course of improvement of left ventricular function for a period of one month. We believe that the proposed studies will provide important information needed for the better management of patients who cannot be weaned from cardiopulmonary by-pass at the present time with the best of techniques and for patients who had a major myocardial infarction with damage of more than 30-40 percent of the left ventricular muscle and are in severe cardiogenic shock. BIBLIOGRAPHIC REFERENCES: Kurusz, M., Stover, L.R., Rosenberg, G., Donachy, J.G., and Pierce, W.S.: Scanning electron microscopy of prosthetic ventricles used for left ventricular assist/total artificial heart devices: Preliminary findings. Scanning Electron Microscopy, 2:221-228, 1977. Migliore, J.J., Rosenberg, G., Prophet, G.A., Landis, D.L., Donachy, J.H., and Pierce, W.S.: Effectiveness of mechanical left ventricular assist pump in acute myocardial failure model. ACEMB, 1977, in press.